Description

The classes CumulativeProtocolDecoder and ProtocolCodecFilter (there are others too, but these two are the important ones for our project) have members of type AttributeKey declared as:
private final AttributeKey ENCODER = new AttributeKey(ProtocolCodecFilter.class, "encoder");

As can be seen, these are not static, so each time ProtocolCodecFilter is created, AttributeKey objects get created as well, which in turn involves creation of a lot of String and char[] objects. jProfiler indicates that AttributeKey is accountable for creation of about 85% of all Strings and char[] in runs of our project, so it makes a significant difference for us.

Is it OK for these attribute key objects to be singletons? If not, what would take to make them singletons?
Some of other MINA filters have AttributeKeys as static members (e.g. MdcInjectionFilter, SslFilter).

To summarize: the improvement being requested is to make the pre-defined AttributeKey objects static within classes such as CumulativeProtocolDecoder and ProtocolCodecFilter.